Method of selectively weakening crimped polyester filaments and fibers



Nov. 29, 1966 G. L. GOULDING ETAL 3,287,787

METHOD OF SELECTIVELY WEAKENING CRIMPED POLYESTER Filed Sept. 29, 1961FIGJ.

DIFFERENCE IN BREAKING LOAD DIFFERENCE IN BREAKING LOAD BETWEEN CRIMPEDAND UNCRIMPED FIBRES FILAMENTS AND FIBERS 5 Sheets-Sheet 1 EFFECT OFCONCENTRATION ALL TREATMENTS FOR HOURS AT ROOM TEMPERATURE o l I 0 IO 203O CONCENTRATION OF NoOH ("/0 W/v EFFECT OF TIME ALL TREATMENTS IN 6()2070 WI! NOOH AT ROOM TEMPERATURE 0 v I I I TIME OF TREATMENT (HOURSGEOFF/M Y 1 (fa/mm 6001 00m ATTORNEYS I O I 5 IN VENTORS 1956 G.GOULDING ETAL 3,287,737

METHOD OF SELECTIVELY WEAKENING CRIMPED POLYESTER FILAMENTS AND FIBERSFiled Sept. 29, 1961 5 Sheets-Sheet so DIFFERENCE m BREAKIN e LOADBETWEEN CRIMPED AN 2O EFFECT OFTEMPERATURE UNCRIMPED FIBRES TIME OFTREATMENT ADJUSTED To GIVE APPROX EQUAL UNCRIMPED o I l I I TEMPERATUREOF TREATMENT o I00 A F164.

EFFECT OF TIME DIFFERENCE IN BREAKING LOAD 60- 20 %N0OH CONTAINING l%BETWEEN c mp LAURYL- DIMETHYL BENZL AND AMMONIUM CHLORIDE AT UNCRIMPEDFIBRES ROOM TEMPERATURE.

INVENTORS TIME OF Tgg ggmT Nov. 29, 1966 G. GOULDING ETAL 3,287,787

METHOD OF SELECTIVELIY WEAKENING GRIMPED POLYESTER FILAMENTS AND FIBERSFiled Sept. 29, 1961 5 Sheets-Sheet 5 FIG.5.

//v VE/I/TO/PS GEOFFREY 4 [mm/70 GUUZDl/VG KEITH Ply/z /P 519m? UnitedStates Patent 3,287,787 lVIETHOD 0F SELECTIVELY WEAKENIN G CRIMPEDPOLYESTER FILAMENTS AND FIBERS Geoffrey Leonard Goulding and KeithPhilip Barr, both of Harrogate, England, assignors to Imperial ChemicalIndustries Limited, London, England, a corporation of Great BritainFiled Sept. 29, 1961, Ser. No. 141,791 Claims priority, applicationGreat Britain, Sept. 30, 1960, 33,612/ 60 8 Claims. (Cl. 28-76) Thisinvention relates to the manufacture of improved fibres and fabrics madetherefrom.

Some fabrics containing staple fibres of natural or synthetic originparticularly when made from polyesters such as polyethyleneterephthalate show a tendency to form small balls of fibres or pills ontheir surface, due to wear. The propensity of forming such balls offibres during wear is known as pilling and is believed to be associatedwith the migration of the fibres which are not firmly held in positionin the yarn or fabric. Pilling is therefore encountered in low twistyarn and in loosely woven or knitted fabrics containing such yarns, whenmade from polyester fibres.

It is an object of our invention to provide improved fibres which can bemade up into fabrics in which pilling is reduced or at least becomesless noticeable, even when low twist yarns and loosely woven or knittedfabrics containing such yarns are used. We have made the observationthat polyester fibres can be weakened at intervals by chemical means ifthey have been deformed by crimping so that they subsequently breakunder mechanical stress e.g. as encountered during wear of the fabric.As a result any loosely held fibres which migrate to the surface of thefabric are broken at the weakened intervals and the formation of pillsis eliminated or reduced and any pills which are formed can be easilyremoved from the fabric surface by applying mechanical stress e.g. bybrushing.

It is another object of our invention to produce tows of polyesterfilaments which can be converted into tops by a stretch breakingprocess, known as tow to top-conversion, in which the forces necessaryfor breaking the filaments are less and breaking is facilitated.Overlengths during cutting are eliminated.

The invention is illustrated in part by the drawings which are graphsshowing the effects of variables in the chemical treatment includedtherein.

FIG. 1 shows the effect of concentration;

FIG. 2 shows the effect of time;

FIG. 3 shows the effect of temperature; and

FIG. 4 shows the effect of time when a quaternary ammonium salt isincluded in the bath.

FIGURE 5 is a diagrammatic plan view of a part of a polyethyleneterephthalate filament being strained by bending, the view being usefulin imparting an understanding of the point of selective pronouncedattack of the chemical agent according to the present invention.

According to our invention, we provide improved crimped filaments andfibres characterised in that they have been weakened at intervalscorresponding substantially to the apexes of their crimp when the crimpis caused by a permanent deformation involving compression beyond 1 to2% of the elastic limit on the inner curvature of the bent filament orfibre. Preferably the ice fibres have 5 to 18 crimps per inch. It isalso preferred that the fibres should be reduced in strength by at leastone third at the apexes of their crimp, compared with the stronger fibreportions between said weaker portions.

We also provide a process for making such filaments and fibres whereincrimped synthetic polyester filaments or fibres are treated with achemical agent under conditions such that the filaments or fibres areweakened at intervals corresponding to the apexes of their crimp. Theprocess is preferably applied to filaments in the form of a crimped,drawn tow before the filaments have been subjected to a heat settingprocess for setting the imparted crimp and before cutting or breakinginto staple fibre.

Many chemical agents may be used, the most convenient are alkalinesolutions such as sodium hydroxide solution, ammonia, solutions ofcertain quaternary ammonium salts or methyl alcohol, which may be addedto the sodium hydroxide solution, or certain diamines such as a solutionof hexamethylene diamine, anhydrous glycols including high molecularweight glycols their esters and ethers, which are still liquid at roomtemperature. Inert diluents may be added to these solutions if desired.

Our invention also provides improved fabrics characterised in that theycontain at least a proportion of crimped polyester fibres which areweaker at intervals corresponding substantially to the apexes of theircrimps. Such fabrics have a reduced propensity to pilling even when theyare made from yarns or using fabric constructions, which when made fromor applied to yarns of unweakened fibres, show a marked propensity topilling.

A treatment of uncrimped filaments or crimped but heat set filamentsunder the same conditions does not lead to the same weakening at spacedintervals along the lengths of the filaments or fibres, because thechemical agents attack more uniformly. It should be appreciated that theweakening or breaking of the filaments or fibres by our treatment is adirect consequence of the selective intensity of the attack caused bythe agents at intervals along the filaments or fibres at the apexes ofthe crimps, whereas the portions between the apexes are affected to alesser degree or may remain substantially unaffected by the uniformapplication of the chemical agent. As a result the portions of thefilaments or fibres treated with a suitable agent break under mechanicalstress preferentially at intervals, whereas the portions between mayremain substantially unaffected in strength.

It is believed that the selected weakening at the apexes of the crimpsis brought about by internal stresses causing local disorder in thefilaments or fibres imparted by the acute deforming operation duringcrimping. For this reason stulfer box crimping and gear crimping arepreferred.

The conditions of treatment have to be determined by experiment andshould be selected so that no intolerable weakening of the filaments orfibres should occur in the uncrimped portion, whereas the apexes of thecrimps are weakened by at least one third or preferably by about onehalf or more, compared with their original strength. This can be done bymeasuring the tenacity of a small sample of the filaments or fibresbefore and after the treatment and by examining the broken ends of thefibres which should occur only at the apexes of their crimp.

The strains introduced during crimping should preferably be such as tocause bending of the filaments at defined intervals and which results ina permanent deformation involving compression beyond l%2% of the elasticlimit on the inner curvature of the bent filament and a tension on theouter curvature of the bent filament to cause adeformation not beyond 5%of the elastic limit, only at intervals along the filament axis. In thecase of polyester filaments having a substantially circular crosssectionthe deformation should preferably involve bending the filaments atintervals to a curvature which is less than 50 times the filamentdiameter, e.g. a 4 denier filament should be bent to a radius ofcurvature of less than 2 times cm. Conditions of crimping shouldpreferably be arranged so that the intervals between crimps result in5-18 crimps per inch. If the crimp frequency is below 5, the crimpedfibres which migrate to the surface of the fabric may cause the fibresto be broken off at intervals which are too large to prevent theformation of pills. In other wonds the projecting broken fibre ends willbe too long to prevent the formation of pills. If on the other hand thecrimp frequency is allowed to rise above 18 crimps per inch, the usefullengths of fibre between the apexes of the crimps may be too short andfabrics made from such fibres are likely to have a reduced resistance toabrasion and Wear and therefore will deter from their commercial value.

For a better understanding of the above requirements we refer to FIG. 5showing a diagrammatic plan view of a part of a polyethyleneterephthalate filament being strained by bending. In FIG. 5 a filamentof diameter d is being strained by bending to a radius r such that asmall part of the filament AB, which part is of the order of thefilament diameter d, subtends an angle at the centre of curvature. Atthe inner curvature of the filament, compression beyond 1%2% will causea permanent deformation and disorientation of the fibre forming polymer.This is believed to permit the selective pronounced attack of thechemical agent compared with the remaining portions of the fibre,because of a rednction in the order of the filament structure in thebent portion.

On the outer curvature an elongation occurs which causes furtherorientation. Because of this, the disorientation at the inner curvatureof the bent filament, the latter becomes prone to greater attack by thetreating agents. On the outer curvature bending will cause orientationwhich may be accompanied by crystallisation and for these reasons theelongation deformation should preferably not be allowed to rise beyond5% and heating before the chemical treatment should likewise be avoided.This therefore defines the amount of strain caused by the bending of thefilaments. As stated, bending of the filament should preferably becaused to be less than 50 filament diameters to fulfil the aboverequirements according to the formula:

The desired crimp may be obtained using a stufi'er box crimper havingrelatively large diameter feed rolls and by adjusting the pressure inthe stulfer box from which the exit of the crirnped filaments isrestrained by means of a dead Weight or by hydraulic pressure. We havefound feed rolls of 46 diameter about 1" wide suitable for the crimpingof tows of 100,000-300,000 denier, in a stuffer box crimper.

It should be appreciated that a uniform application of the chemicalagent is necessary in order to obtain the selective weakening of thefilaments according to our invention. Strong aqueous caustic alkalisolution of 20- by weight, may be used at low temperatures, for exampleat 20-40 C., for a treatment lasting 30-50 hours. The addition of smallamounts of catalytic accelerators to the caustic alkali solutionselected from methyl alcohol and certain quaternary ammonium salts,speed up the reaction. Suitable quaternary'ammonium salts comprise e.g.,cetyl trimethyl ammonium bromide and lauryl dimethyl benzyl ammoniumchloride. The effect of other quarternaries such as cetyl trimethylpyridinium bromide, dimethyl phenyl benzyl ammonium chloride andtetramethylammonium bromide is less marked, and because of theadditional cost to the treatment they are therefore not recommended.With the addition of the accelerators the concentration of the causticalkali solution may be considerably decreased e.g., to 5% by weight oras low as 1%. Using temperatures nearthe upper limit as specifiedhereafter, the time of the treatment may be drastically reduced. Quitesmall amounts of the accelerator are suitable e. g., 0.005% to 1% byWeight of the solution, as described in our copending US. Patent 3,135,-577. It must be emphasised, however, that the treatment should becarried out at a temperature below heat setting temperature to obtaineffective treatment. It will be appreciated that the time of treatmentcan be shortened as higher temperatures are used, but since theselective degradation of the crimped filaments decreases with increasingtemperature, temperatures below 110 C., preferably room temperature upto about C. are preferred.

In the case of crimped filaments having an overall tenacity above 4 gms.per denier the tenacity should be reduced preferably below 3 and about1.5 g.p.d. In the case of medium tenacity fibres below 4 gms. per denierit is desirable to reduce the overall fibre tenacity to 2.5 gms./denieror below but above 1.0 gm. per denier. It will be appreciated that acertain amount of reduction in the tenacity even in the stronger fibreportions, between the crimps, i tolerable but this should preferably notexceed of the initial tenacity. In the case of the treatment withcaustic alkali a loss in weight of up to 10% with a correspondingreduction in the diameter of the filaments may be brough about and thisis associated with an improved handle of the fabric.

Our invention will more particularly be described relating to polyesterfilaments and fibres made from polyethylene terephthalate for which itis particularly suitable, the filaments having a substantially circularcross section. It will be appreciated, however, that our invention isnot intended to be so limited and that it applies also to filaments andfibres having a non-circular cross section, particularly a cruciform,Yshaped, tri-lobal, dogbone, or any other known cross section forthermoplastic filaments. Similarly it will be applicable to otherpolyester or copolyester filaments as stated earlier and which show apropensity to pilling.

Preferably polyethylene terephthalate filaments are produced by aprocess of melt spinning followed by drawing at a temperature below 110C. preferably between and 98 C. The drawn filaments in the form of towsare then subjected to a stutter box crimping operation ensuring adeformation in the filaments to cause bending at intervals to acurvature which is less than 5 0 times their filament diameter in orderto impart the desired crimp, at a frequency of between 5 to 18 crimpsper inch, depending upon the filament diameter which may be between 1 to5 denier per filament.

The crimped tows are then subject to the treatment with the definedchemical agents which are removed by e. g., neutralising with dilutestrong acid solution, rinsing with water, followed 'by drying and heatsetting'at a temperature above C., preferably using steam atsuperatmosphen'c pressure. and temperatures between -l50 C., andtemperatures up to 220 C. using dry heat. Setting is necessary to bringresidual shrinkage in boiling water for 1 minute, to less than 1%.

Suitable finishing lubricants may be applied before or after heatsetting in order to facilitate processing and to prevent theaccumulation of static electricity. The crimped, treated and heat settows are then cut into staple fibres of the desired length, e.g.,between 1 /2" and 7".

From these staple fibres improved fabrics can be produced by knownmethods comprising weaving and knitting; such fabrics have a reducedpropensity to pilling. We also provide a new type of synthetic polyesterfibre having 5-18 crimps per inch and an overall tenacity,

of 2.5 gms. per denier or below, but above 1.5 g.p.d., the tenacity ofthe stronger portions of the fibre, between the apexes of the crimp,being only up to /3 less than the initial tenacity of the drawn fibres.By comparison the drawn crimped fibres have a tenacity of 4 gm. perdenier and up to 6 gm. per denier, before the treatment with thechemical agent.

The polyester filaments and fibres referred to in this specification aremade by a process of melt spinning and denote fibre forming polyestersincluding polyethylene terephthalate, copolyesters derived from up to15% of another component which may be selected from the group ofdicarboxycylic acids having the formula:

HOOC-RCOOH where R may be methylene, polymethylene or arylene, otherthan paraphenylene, represented by a sebacic, adipic and isophthalicacid, and the remainder polyethylene terepht-halate; or modified fibreforming polyesters such as po1y(hexahydropar-axylylene)terephthalate.

The filaments may be subjected to a deformation step which is effective,followed by the treatment with a suitable agent and if desired followedby further steps such as heat setting before or after furtherdeformation steps to bring about a greater crimp frequency. Thefilaments Example 11 between 2% and 6 inches.

need not be cut and may be made up into fabrics from our treatedfilaments in the form of filament yarn.

If the filaments or fibres in their specified crimped condition are tobe treated in fabric form, no heat setting of the imparted crimp musttake place after crimp ing and prior to the treatment. I

The polyester filaments may be subjected to immersion or spraying withhot substantially anhydrous polyethylene glycols and nonyl phenylpolyethylene glycol ethers, of a molecular weight of 200-2000, usingtemperatures above 80 C. but at least 30 C. below the meltingtemperature of the polyester, preferred temperatures are 110-130 C. Thepolyglycols may be applied before or after drawing of the polyesterfilaments and this brings about a considerable improvement in dyeuptake. One such application of polyglyc-ols is described in ourcopending US. application Serial No. 114,021.

The following examples in which all parts and percentages are by Weightillustrate but do not limit our invention.

Example I A 275,000 denier tow containing 70,000 filaments ofpolyethylene terephthalate is crimped in a stuffer box crimper so thatthe tow has 10-14 crirnps per inch. The crimped but unset tow is treatedby immersion in a 22.5% sodium hydroxide solution in Water at 30 C. for40 hours. Excess solution is removed between squeeze rolls and the towis washed with water, dried and heat set with steam at 130 C., and cutinto staple fibres of any desired length. When a number of filamentsfrom the treated tow are tested in a tensile testing apparatus, it isfound that breakage occurs always at the apex of the crimp, and thesingle fibre tenacity compared with an untreated control is reduced by94%. Fabrics containing the treated staple fibres show no pilling, whereas fabrics containing untreated fibres show munerous pills.

The single fibre tenacity of crimped tow which is heat set using steamat 140 C. for half an hour, before the treatment with the sodiumhydroxide solution in Example I, is reduced by only 32%.

Conversion of the tow into top or yam is facilitated as lower stretchingforces are required, because the alkaline treatment has producedpositions of low tensile strength at the apexes of the crimps and thetow will break to give the required fibre length more easily.Undesirable overlengths and underlengths in the staple fibres willtherefore be absent.

In the following Example III to VI, experiments are described toillustrate the effect of setting on a simulated crimp in polyethyleneterephthalate yarn under various treating conditions with caustic sodasolutions, with and without an accelerator, and the testing method usedfor determining the breaking load and extension of the yarn.

Yarn: Polyethylene terephthalate Terylene 75 denier 36 filament yarnhaving a tenacity of 4.5-5.5 g.p.d. and an extension at break of 27-17%.

Crimping: The yarn was wrapped around a 2 centimeter wide strip ofcopper foil 0.25 mm. thick, placed between polished steel plates andsubjected to a pressure of 15 tons per square inch for five minutes in ahydraulic press, to obtain a simulated crimped yarn, in which eachfilament is deformed by compression beyond the elastic limit on theinner curvature of the bent filaments, when the elastic limit is between1-2%.

Setting: The yarn was subjected to dry heat setting by a treatment in anelectric oven at 140 C. for ten minutes. Other samples of the same yamwere subjected to steam setting in a Sanderson oven at a steam pressureof 40 lbs. per square inch, equivalent to a temperature of 140 C., forfifteen minutes.

' Treatment: The crimped yarn, set or not set as required, was placedwith an uncrimped control in a ml. flask and treated as described. Afterthe treatment the samples were washed thoroughly in water and dried.

Testing: Lengths of yarn containing one crimp only were mounted oncards, the crimp position marked and the fibre breaking load andextension at break were determined on an Instron tensile tester. Figuresquoted in the following tables are the mean of ten tests.

The uncrimped controls were tested similarly.

Example III Effect of setting the crimps. The results are shown in Table1 in which the treatment time used Was 30 hours using a 20% w./v. sodiumhydroxide solution at room temperature. Unset, dried heat set, and steamset yarns both crimped and uncrimped were tested for breaking load andextension at break both before and after the treatment with causticsoda. It will be seen from the table that the effect obtained producesconsiderable differences in tensile strength between the crimped anduncrimped portion of the filame-nts and that this effect is achievedwith the unset fibre where, after treatment, the crimped fibre was 48%weaker than the uncrimped fibre. The set fibres do not show thissignificant strength difference.

Dry heat set fibre differs by approximately 6% between crimped anduncrimped samples, both before and after treatment. Crimped steam setfibres was twice as weak compared with an uncrimped sample, aftertreatment as before the difference was still only 21%.

In every case the unset treated samples broke at the crimp when tested,whereas the controls and also the set crimped samples did not alwaysbreak at the crimp. A sufficient number of tests have been made toconclude that weakening occurs preferentially at the apex of the crimpin the case of unset filaments.

TABLE L-EFFECT OF SETTING Unerirnped Crimped Percent Difierence YarnBreaking Exten- Breaking Exten- Breaking Exten- Load sion Load sion Loadsion Unset:

Control 355 41. 276 24. 4 40. 5 Treated 283 28 2 147 14. 0 51 Dry HeatSet:

C tr 342 38. 6 319 36. 5 6. 7 4. 9 241 26. 5 227 23. 7 5. 8 10.5

Example IV strength between crimped and uncrimped yarn decreased Effectof concentration.Unset crimped yarn and uncrimped controls as described,were used to investigate rapidly with increasing temperature. This couldbe due to the setting efiect of the hot liquid.

TABLE 4.EFFECT OF SETTING (SEE ALSO FIGURE 3) Treatment UncrimpedCrimped Percent Diflerenoe Temp., Time, Breaking Ext-en- Breaking Exten-Breaking Exten- C. Load sion Load sion Load sion the effect of varyingthe concentration of the alkali and Example Vl the time of treatment.The results are summarised in Tables 2 and 3 (and in FIGURES 1 and 2).The difierence in strength between the crimped and uncrimped fibresincreased both with concentration and with time of treatment.

TABLE 2.--EFFEOT OF CONCENTRATION [Unset yarn treated for 30 hours atroom temperature] Polyethylene terephthalate yarn was treated at roomtemperature with 20% sodium hydroxide solution to which 1%lauryl-dimethyl benzyl ammonium chloride,

available under the trade name Vantoc CL, had been TABLE 3.EFFEC'I OFSETTING Unset yarn treated at room temperature "in 20% w./v. NaOHUnerimped Crimped Percent Difierenee Tirne'oi Treatment Breaking Exten-Breaking Exten- Breaking Exten- Load sion Load sion Load sion Control I329 V 40. 9 21a 24. 4 16.1 40. a

Example V added. The results of the treatment during one to sevenInvestigation of the eifect of the temperature is shown in Table 4 andFIGURE 3. The time of treatment was varied in order to give a constantvalue for the strength of the uncrimped fibres and the results showedthat at 9 hours on uncrimped and crimped filaments is shown and thedifference in tensile properties and the percentage difference betweenuncrirnped and crimped samples are tabulated in Table 5 (and FIGURE 4).It can be seen that after only six hours the crimped yarn was too weakfor treatment temperatures of over C. the difference in the tensilestrength to be measured. If the time for the 9 difference in strengthbetween crimped and uncrimped yarn to reach 50% is compared, the use of1% accelerator (Vantoc C.L.) is seen to speed up the reaction twenty-sixtimes, that is to say, 1.3 hours compared with 34 hours in Example III.

10 and polypropylene, provided that the treatment is carried out with asuitable agent which will attack at the apexes of the crimp and when thecrimp has been obtained by bending under compression beyond the elasticlimit and TABLE 5.EFFECT OF ACCELERATOR (SEE ALSO FIG. 4)

[Unset yarn treated at room temperature with w./v. NaOH containing 1%lauryldimethylbenzylammonium chloride] r Example VII This exampleillustrates the effect of the treatment on pilling. A stuffer boxcrimped unset drawn polyethylene terephthalate tow was treated forthirty hours in 20% aqueous sodium hydroxide solution at roomtemperature, washed with water, dried, set in air at 140 C. for 10minutes, out into 2 inch lengths and resulting staple fibres wereconverted on standard cotton equipment to give spun cotton typepolyester yarn and this was woven into a twill fabric which was testedfor pilling.

Table 6 shows the properties of the fibre at various stages of fabricproduction, compared with untreated polyester cotton-type 2" long staplefibres. It will be seen that improved pilling performance is achieved atthe expense of decreased flex abrasion resistance and tensile strength.The lower extension at break of the treated fibre is of not set, so thatthe filaments and fibres are weakened at intervals corresponding to theapexes of their crimp.

The Brush and Sponge test referred to in Example VII is described inA.S.T.M. 1958 D. 1375-55T, page 515. This test is intended to determinethe resistance of Woven fabrics to pilling and fuzzing. The methodprovides a laboratory procedure for mechanically simulating wearconditions by first brushing a fabric to form free fibre ends and thensubjecting the fabric to a circular rubbing action with a sponge whichrolls the fibre ends into pills.

What we claim is:

1. A process for treating crimped oriented polyester filaments andfibres, before heat setting the crimp, with a chemical agent underconditions such that the filaments and fibres are selectively weakenedat intervals corresponding to the apexes of their crimp by the uniformapplication of the chemical agent, the filaments and fibres particularadvantage if the fibres are blended with cotton. between said intervalsbeing substantially less affected by TABLE 6.FAB RIC P RODUCTIONProduction Details Fibre Form Property Units Untreated Treated FibreFibre Cut Fibre 1. Fibre length Inches :2 2 3 G.p.d 5. 37 2. 38Ertznsion Percent 30 18 Spinning Fibre spun into 2l18.7s 0.0. Singlesyarn (1/18.7s) Tenacity G.p.d 2. 42 1. 42 yam with 102 singles and 5Sdoubling Extens1on Percent, 30. 3 17. 7 twist. Doubled yarn (2/18.7s)Tenac1ty... G.p.d 2. 77 1. 45 Extension Percent 32. 2 17,9

Weaving Yarn woven into a 2/2 twill Finish, Fabric Pllling {sponge testPills/sq. in 28 8 fabric 32' wide 52 x 52 ends x picks/inch 200 nuns).finished sett.

Flex abrasion No. of flexes 6, 000 1, 800 to break.

Flat abrasion SimLar It will be seen from the examples that:

1) Unset crimped fibre is preferentially attacked at the crimp apexes bystrong aqueous caustic soda solution.

(2) Both steam and dry heat-set crimped fibres do not undergo thispreferential attack to the same extent.

(3) Addition of quaternary ammonium salts to caustic soda solutionaccelerates the rate of attack.

(4) Fabric made from treated fibre shows an improvement in pillingperformance compared with untreated fibres.

Although in the preceding examples polyethylene terephthalate filamentsand fibres have been use, it is believed that similar effects areobtained with other commercially available crimped oriented hightenacity synthetic polymer filaments or fibres such as nylon, Perlonsaid chemical agent whereby the fibers and filaments are predisposed tobreak in said intervals.

2. A process for treating crimped oriented polyester filaments accordingto claim 1 in the form of a crimped tow after drawing, followed bycutting into staple fibre lengths and heat setting the crimp to reduceresidual shrinkage, in boiling water for one minute, to less than 1%,said heat setting being carried out after the treatment.

3. A process for treating crimped oriented polyester filaments accordingto claim 1, in the form of a crimped tow after drawing followed bystretch breaking the filaments by a tow to top-process and heat settingthe crimp to reduce residual shrinkage, in boiling water for one minute,to less than 1%, said heat setting being carried out after thetreatment.

4. A process according to claim 1 in which the filaments are crimped byintroducing a compressed strain on the inner curvature, this compressingstrain being beyond the elastic limit in compression, through bending toa curvature which is less than 50 filament diameters according to theformula:

Where d is the filament diameter, r is the radius of bending, s is theangle subtended by an element of the filament at the centre ofcurvature.

5. A process for treating crimped oriented polyester filaments andfibres according to claim 1 in which the chemical agent is an alkalinesolution comprising sodium hydroxide.

6. A process for treating crimped oriented polyester filaments andfibres according to claim 1 in which the chemical agent comprises atleast one of the following: sodium hydroxide, ammonia, certainquaternary ammonium salts, methyl alcohol, hexamethylenediarnine,polyethylene glycols, and nonyl phenyl polyethylene glycol ethers.

7. A process according to claim 1, in which the chemical agent comprises530% aqueous sodium hydroxide solution.

12 8. A process according to claim 1 in which the chemical agentcomprises sodium hydroxide and 0.005 %1% by weight of a quaternaryammonium salt selected from cetyl trimethyl ammonium bromide and lauryldimethyl benzyl ammonium chloride.

References Cited by the Examiner UNITED STATES PATENTS 2,781,242 2/ 1957Knapp 28-1 2,828,528 4/1958 Gajjar 28-1 2,897,042 7/1959 Heiks 8-13012,907,094 10/1959 Murray et a1. 28-76 2,999,296 9/1961 Breen et a1 28-783,034,196 5/1962 Bohmfolk 28-82 FOREIGN PATENTS 1,024,482 2/1958Germany. 1,033,175 7/1958 Germany. 1,03 4,133 7/ 1958 Germany.

840,796 7/ 1960 Great Britain.

MERVIN STEIN, Primary Examiner.

DONALD W. PARKER, ROBERT R. MACKEY,

Examiners.

H. G. GARNER, L. K. RIMRODT, Assistant Examiners.

1. A PROCESS FOR TREATING CRIMPED ORIENTED POLYESTER FILAMENTS ANDFIBRES, BEFORE HEAT SETTING THE CRIMP, WITH A CHEMICAL AGENT UNDERCONDITIONS SUCH THAT THE FILAMENTS AND FIBRES ARE SELECTIVELY WEAKENEDAT INTERVALS CORRESPONDING TO THE APEXES OF THEIR CRIMP BY THE UNIFORMAPPLICATION OF THE CHEMICAL AGENT, THE FILAMENTS AND FIBERS BETWEEN SAIDINTERVALS BEING SUBSTANTIALLY LESS AFFECTED BY SAID CHEMICAL AGENTWHEREBY THE FIBERS ARE FILAMENTS ARE PREDISPOSED TO BREAK IN SAIDINTERVALS.